1. Field of the Invention
The present invention relates to a signal waveform displaying method and an apparatus for it, and more particularly, to a displaying method and an apparatus capable of editing waveform data.
2. Description of Related Art
In a conventional signal waveform display method, the waveform display operation for a signal, e.g., a digital signal is performed uniformly all over the time period while the signal extends. Therefore, in order to observe the portion of waveform outside of a display window, the scroll operation needs to be repeated or the whole of the signal waveform needs to be compressed at a constant ratio with respect to the time axis.
In another conventional signal waveform display method, signals are inputted with a predetermined sample period of time and the waveforms at two adjacent sample periods are compared with each other so that the waveforms are displayed only when there are changes between the waveforms at the two adjacent sample periods. Such a method is disclosed in Japanese Patent Application Laid Open No. 60-6874, for instance. In the method, when signals shown in FIG. 5 are inputted, the signal waveforms are displayed as shown in FIG. 1.
However, in a case where the change of signal waveforms is to be observed, if the scroll operation of a display window is performed in order to compare a portion of the signal waveform with another portion thereof apart from the portion, there is a problem that the comparison is very difficult and the scroll operation requires a long time. Also, if the signal waveform is compressed with a constant ratio, there is another problem that the signal waveform is compressed below than the resolution of a display unit so that the signal waveform is deteriorated.
As shown in FIG. 1, if only the changes of signal waveforms are displayed, there is caused still another problem that the time-varying characteristics of the signal waveform cannot be observed.